Conventionally, a machining process, called chamfering, is generally carried out on the periphery of a semiconductor wafer so as to prevent chipping or cracking from occurring during the process of manufacturing a semiconductor device. The method of chamfering includes a method of machining the periphery of a semiconductor wafer into an arcuate shape such that a surface on which an epitaxial film is grown (hereinafter referred to as “the main surface”) and a back surface are connected by a smooth curve, and a method of machining the periphery of the semiconductor wafer into a tapered shape such that the main surface and the back surface are prevented from meeting an end face of the periphery at right angles. Particularly when the periphery is machined into an arcuate shape, the main surface and the back surface of a semiconductor wafer are connected by a perfect smooth arc, which is very advantageous in preventing cracking or chipping from occurring in the periphery of the wafer.
The semiconductor wafer thus chamfered has the main surface alone or both the main and back surfaces mirror-finished, and then has an epitaxial film of one of various compositions grown on the main surface.
However, when the semiconductor wafer chamfered by such a method as described above and having the main surface side thereof mirror-finished is used as a substrate to grow an epitaxial film on its main surface, a normal epitaxial film is formed on the main surface and a portion of a chamfered portion toward the main surface, but an extraordinary growth without monocrystallinity sometimes occurs in a portion of the chamfered portion toward the periphery of the wafer. Further, due to a distortion caused by the extraordinary growth and a distortion inherent to the grown epitaxial film, wedge-shaped defects, called microcracks, sometimes occur, which extend from the extraordinary growth to the epitaxial film.
Then, with the distortion inside the crystal or the wedge-shaped cuts (microcracks) as a start, the substrate is sometimes broken after the epitaxial growth. It should be noted that occurrence of such a phenomenon tends to be marked with an increase in the thickness of the epitaxial film.
The present invention has been made to provide a solution to the above problems, and an object thereof is to provide a semiconductor wafer which is capable of effectively preventing microcracks from being formed in a periphery of the wafer when epitaxial growth is performed on the main surface thereof, and the wafer from being broken with the microcracks as a start, and a method of manufacturing the same.